1. Field of the Invention
The present invention relates to an apparatus for optically recording and reproducing information, and more particularly to an apparatus as above for use with a card type optical information recording medium.
2. Description of Related Background Art
As an optical information recording medium of this type there is known a so-called write-once type optical card capable of recording information once and reproducing the recorded information plural times. In recording information in a write-once type optical card (hereinafter simply called an optical card), a light beam modulated by the information to be recorded is converged into a fine light spot by using a lens. The fine light spot (hereinafter simply called a light spot) is applied onto an information recording area of the optical card while scanning it along the information recording area. The information is accordingly recorded in the optical card as a pit train (information track) optically detectable, e.g., based on a difference of light reflectance between the pit area and the other area. In reproducing the recorded information, a light spot having less optical energy than that used for the recording is applied onto the information track while scanning it along the track. The reflected light from the information track is detected to reproduce the recorded information.
An optical head is generally used for recording/reproducing information while applying a light spot onto an optical card. Either an optical head or an optical card is reciprocally moved in order to conduct light beam scanning. However, an optical head is a precision instrument constructed of a number of optical components and drive elements so that it has a poor resistance against impact motions such as rapid acceleration and deceleration. An optical card should be maintained so as to have no warp and held in position on a shuttle with as small a setting error as possible. Therefore, the shuttle is sufficiently strongly constructed to press an optical card and adjust warp or the like to some degree, resulting in a limit to making it light-weight. In view of the above, it is difficult to reciprocally move an optical head or an optical card (shuttle), whichever may be, at high speed. Thus, it has been difficult to realize high speed information recording/reproduction.
Reproducing information in particular is carried out frequently and repeatedly so that there is much demand for high speed reproduction which the conventional background art cannot provide.